Variable resistor device



Dec. 28, 1937.

E. SEVERIN El AL 2,103,873

VARIABLE RESISTOR DEVICE Filed April 22, 1936 INSULATION INVENTORS EDWIN SEVERIN AND ATTORNEY.

Patented o... 28,1937 I 2,103,873

.VARIABLE RESISTOR DEVICE Edwin Severin and Friedrich Schierl, Berlin, Germany, assignors to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application April 22, 1936, Serial No. 75,688 In Germany April 13, 1935 4 Claims. (Cl. 201-48) The invention relates to a variable resistor grooves of the counter contacts. As tests have characterized by the novel design of the elements shown, even when a considerable amount of dirt establishing the contact. The novel resistor is settles on the contact surface, the voltage divided used with preference in apparatus for wireless still operates without objection, since the dirt par- 5 communication. ticies at operation of the voltage divider glide The known variable resistors in which the tapfrom the projections into the grooves or they are ping of the current is not carried out across nonpressedthereinto, so that the projections are algliding contact members such as yielding contact ways in continuous contact with the metal of the members with rolling movement, have the distake-off contact.

advantage that between the resistor and the con- Neither does oxidation of the contact surface 10 tact rolling thereon, dust particles may easily be cause an interruption, since the oxide layer will deposited and which when operating the voltage be destroyed during the switching performance. divider will be pressed down upon the surface of This is due to the fact that owing to th 'the resistor or upon the contact where they cause ing of the contact surface, the specific pressure an interruption between contact and the resistor. upon th individual su pa ts of th unt r 15 .Similar conditions exist in voltage dividers in contacts becomes so high t t O d layer which special contacts are provided between reeventually fo W again be torn p sistor and take-off contact. In the known struc- Hence, a favorable pas Current we tures, these contact members consist of wires take-off contact and counter contact will always embedded at certain distances in the carbon rebe assured. 20

sistor and fixedly joined therewith. The free The new type of resistors was found to be espeends of the wires are bent around a separate supcially advantageous in.resistors with radially arpo t ng body. The take-oil contact, ordinarily ranged contacts and in which, as take-01f cona tumbler disk of conducting metal, glides in a tact, a SO-Called tumbler d sk is used.

5 rolling movement in the known manner on the Bet the mp iv y large Counter surface or these wire ends in this way establishtacts, special resistors can be interposed in the ing the connection between the take-off co tact form of fixed single resistors, and which are not and the resistor. v influenced by atmospheric conditions. Thus the Since the surface of each wire piece making hitherto customary carbon resistors with open 3!) contact with the take-off contact is comparasurface, which proved to be very unreliable in tively large, also in this case dust particles dep n, are Omittedposited on th surface of t i produce Variable resistors having fixed resistance stages turblng effect. are already known. In these resistors the take- If the wire becomes oxidized there likewise oco contacts w f rme as gli in ntac s curs an interruption of the contact between th pressing against the counter contacts under their take-oil? member and the resistor. Even where own sp g action- It was hereby found. that the the take-off contact at the respective place of tapbronze sheets gliding over the contacts lose their plug is under a high pressure, the specific presp y action C1116 to e. thus no longer sure on the wireis low owing to the comparatively exerting the ss ry p ssure on the contacts.

large surface, and this prevents the splitting of The bronze .brushes sometimes used scraped 40 the oxide layer deposited on the wire surface. small filings from the contact surfaces which in Hence, complete interruption between the'coopturn out grooves into the contact pieces which crating contact occurs. 1 detrimentally affected the establishing of con- To eliminate the disadvantages of these known tact. Irrespective of the soiling of the contacts resistors, in acordance with the invention, the and of the bronze brushes a favorable current 45 surface of the contacts connected to the resistor passage between the brushes and the contacts can and making direct galvanic connection during no longer be maintained. There occur the sooperation with the take-off tumbler disk, or in called loose contacts between the two layers which case of elongated resistors, a band-shaped, elastic are very detrimental to proper operation. element, are totally or partially roughened or Y, .The interposing of a tumbler disk or similar 50 provided with grooving. It is hereby accomelement in resistors deviating from the circular 'plished that at the rolling movement of the takeshape overcomes this disadvantage. The presoff contact on the counter contacts practically sure piece for the moving disk is preferably not taking place without friction, dirt particles deconstructed at the same time as the current takeposited between said organs are pressed into the oil.

An embodiment of the invention is shown in various figures in the accompanying drawing.

Figure 1 shows a variable resistor in the form of a voltage divider in a top view, and wherein the contacts are disposed radially, Fig. 2 shows an elevation thereof and, Fig. 3 is a top view showing the construction of the contact surface.

The base plate [consisting of insulating mateiial has the resistance contacts 2 fastened thereto. Opposite these contacts there is situated the flexible disk or contactor 3. This contactor 3 is designed as a tumbler disk, and it is pressed down upon resistor contacts 2 by means of arm or lever and pressure member 5. Lever a is rotatably mounted about a control shaft 6. The contact disk 3 is mounted between insulating pieces 1 and 8 whereby an electric connection between the.

contactor 3 and the shaft 6 is avoided. In this manner it is accomplished that undesirable actions upon the voltage divider due to the capacity of the hand are eliminated during the operation of said voltage divider. Since the contact disk is arranged separately from the pressure piece 5, the lever preferably consisting of spring steel provides a ready means for exerting any desired pressure upon the contact disk. The surface of the resistor contacts 2, as far as the contact surface is concerned, is provided with grooves Q or the like. The surface of the grooving 9 is obliquely disposed relative to the shaft 6 to provide inthis way a contact surface for the contactor that is as large as possible. The distance I0 between the contacts2 is comparatively small, thereby obtaining a smooth transition from one contact stage to the other one. The resistances H diagrammatically shown in the drawing are interposed between the contacts 2. In order to prevent unnecessary deposit of dust particles on the voltage divider, it is advisable to enclose the latter entirely. At the same time, electrical and magnetic disturbances through outer fields are thereby avoided.

Instead of groovings and the like in the resistance contacts, the surface thereof may be smooth and the disk 3-may then be provided with grooving. In certain cases it may be of advantage to roughen the surfaces of both cooperating contacts i. e. the surface of the resistance contacts, as well as that of the member 3.

Having described our invention, what we claim as novel and desire to secure by Letters Patent is:

1. In a variable resistor, thecombination of a rotatable shaft, a plurality of contacts having their surfaces formed with a plurality of grooves, a flexible conducting member normally separated from said contacts, stationary insulation discs in contact with the opposite faces of said flexible member and serving to retain it in a fixed position and an arm carried by said shaft and arranged to force a limited area of said conducting member into contact with one of saidgrooved surfaces.

2. In a variable resistor, the combination of a rotatable shaft, a plurality of contacts having their similar surfaces formed with a plurality of intersecting grooves, stationary insulation members surrounding said shaft, a flexible conducting member normally separated from said contacts and fixedly secured between said insulation members, and an arm carried by said shaft and arranged to force different portions of said conducting member successively into contact with said grooved surfaces.

3.iIn a variable resistor, the combination of a rotatable shaft, a plurality of contacts having their adjacent edges separated by a small amount I and having their corresponding faces provided with a plurality of cut-out portions, a plurality of resistors each connected across the adjacent endssaid contacts, said yielding member being fixedly mounted with respect to said contacts, and a resilient arm carried by said shaft and mengagement with said yielding member and arranged to flex successive portions thereof into engagement with the faces of said contacts.

4. In a variable resistor, the combination of an insulating supporting member provided with an opening, an operating shaft passing through said openingf a plurality of concentrically arranged ring sector shaped contacts secured to one face of said supporting member, said contacts being slightly separated and having their exposed faces provided with a plurality of fine intersecting grooves, a flexible conducting member non-rotat ably mounted adjacent said contacts and an arm carried by said shaft and arranged to urge portions of said flexible member into successive engagement with the grooved areas of said contacts.

' EDWIN SEVERIN.

FRIEDRICH SCHIERL. 

